198 MR. JUKES-BROWNE AND PROF. HARRISON 



writing of them as if they were interstratified with the clays and 

 sandstones which are the prevalent rocks of that district. Our 

 examination, on the contrary, has led us to conclude that they are 

 entirely distinct from and newer than these clays and sandstones, 

 though the two series are often brought into juxtaposition by means 

 of powerful faults. 



In accordance with the ideas prevalent at the time he wrote, 

 Schomburgk refers the contortions of the rocks and the upheaval of 

 the island to a volcanic convulsion, and regards the gullies which 

 traverse the Coral Limestone as having originated in a series of 

 ctacks produced by this volcanic convulsion. Prom this view, as 

 might be expected, we most unequivocally dissent. 



ISince the publication of Schomburgk's book, no geologist seems 

 to have examined the island. Prof. Duncan's paper on West-Indian 

 Corals * (1863) will be referred to in the sequel. Meanwhile it 

 will suffice to say that we cannot accept his view that the Coral 

 Limestone of Barbados is of Miocene age. 



Mr. Lechmere Guppy, in his paper on the West-Indian Tertia- 

 riest(1866), refers briefly to Barbados, and points out that no 

 extinct species of MoUusca have been recorded from any of its 

 Coral Limestones. 



Alexander Agassiz, in " The Three Cruises of the ' Blake ' " (1888), 

 makes several references to Barbados, but he did not make any 

 personal explorations on the island, and has unfortunately been 

 misled into stating that it is " a volcanic cone entirely surrounded 

 by coral terraces which completely hide the cone"±; and again, 

 " The trachytic cone forming the base upon which the successive 

 terraces of Barbados have been elevated is seen to crop out on the 

 surface in the north-east part of the island " §. 



As no such mass of trachytic rock had been seen by us, and as 

 we had not found even so much as a dyke of volcanic rock in any 

 part of the island, we wrote to ask Prof. Agassiz what ground he 

 had for his statements. In reply he explained that they were made 

 on the authority of a gentleman in Bridgetown who showed him 

 specimens of trachytic rock obtained from the north of the island, 

 and who assured him that the rock existed in situ ; but he admits 

 that as he did not visit the locality he ought perhaps to have been 

 more guarded in his statements. 



We believe the mistake originated in the following way : — Frag- 

 ments of trachytic rock do occur on the surface-soil in many places, 

 and some of them are nearly as large as a man's fist, but we 

 believe that they have all been imported into the island. Eaw 

 guano brought from the islands off the northern coast of South 

 America has been used as a manure for many years past, and frag- 

 ments of volcanic rocks as large and even larger than a man's fist 



* Quart. Journ. Geol. See. vol. xix. p. 406. 



t Ihid. vol. xxii. p. 570. 



I Bull. Mus. Harvard Coll. p. xix ; see also p. 63. 



I Op. cit. p. 79. 



